Communications device, infrastructure equipment and methods

ABSTRACT

A communications device configured to receive data from an infrastructure equipment of a wireless communications network is provided. The communications device comprises transceiver circuitry configured to transmit signals and to receive signals via a wireless access interface provided by the wireless communications network, and controller circuitry. The controller circuitry is configured to control the transceiver circuitry to receive an explicit uplink hybrid automatic repeat request acknowledgement indicator, e-HARQ indicator, from the infrastructure equipment, and to determine, in accordance with the received e-HARQ indicator, whether or not the communications device should monitor for a first HARQ acknowledgement, HARQ-ACK, in a specific time slot and in a specific frequency resource of the wireless access interface, the first HARQ-ACK being transmitted by the infrastructure equipment in response to an uplink transmission from the communications device to the infrastructure equipment.

BACKGROUND Field of Disclosure

The present disclosure relates to communications devices configured totransmit data to a wireless communications network and to receive datafrom the wireless communications network via a wireless access interfaceusing a transmitter and a receiver respectively, which include anarrangement for providing a feedback message such as an ACK or NACKwhich may be part of an automatic repeat request (ARQ) type protocol.The present invention also relates to methods of communicating usingcommunications devices, wireless communications networks, infrastructureequipment and methods.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architecture, are able to support more sophisticated services thansimple voice and messaging services offered by previous generations ofmobile telecommunication systems. For example, with the improved radiointerface and enhanced data rates provided by LTE systems, a user isable to enjoy high data rate applications such as mobile video streamingand mobile video conferencing that would previously only have beenavailable via a fixed line data connection. The demand to deploy suchnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, maybe expected to increase ever more rapidly.

Future wireless communications networks will be expected to routinelyand efficiently support communications with a wider range of devicesassociated with a wider range of data traffic profiles and types thancurrent systems are optimised to support. For example it is expectedfuture wireless communications networks will be expected to efficientlysupport communications with devices including reduced complexitydevices, machine type communication (MTC) devices, high resolution videodisplays, virtual reality headsets and so on. Some of these differenttypes of devices may be deployed in very large numbers, for example lowcomplexity devices for supporting the “The Internet of Things”, and maytypically be associated with the transmissions of relatively smallamounts of data with relatively high latency tolerance.

In view of this there is expected to be a desire for future wirelesscommunications networks, for example those which may be referred to as5G or new radio (NR) system/new radio access technology (RAT) systems,as well as future iterations/releases of existing systems, toefficiently support connectivity for a wide range of devices associatedwith different applications and different characteristic data trafficprofiles.

Another example of such a new service is referred to as Ultra ReliableLow Latency Communications (URLLC) services which, as its name suggests,requires that a data unit or packet be communicated with a highreliability and with a low communications delay. URLLC type servicestherefore represent a challenging example for both LTE typecommunications systems and 5G/NR communications systems.

The increasing use of different types of terminal devices associatedwith different traffic profiles gives rise to new challenges forefficiently handling communications in wireless telecommunicationssystems that need to be addressed.

SUMMARY OF THE DISCLOSURE

The present disclosure can help address or mitigate at least some of theissues discussed above.

Embodiments of the present technique can provide a communications deviceconfigured to receive data from an infrastructure equipment of awireless communications network. The communications device comprisestransceiver circuitry configured to transmit signals and to receivesignals via a wireless access interface provided by the wirelesscommunications network, and controller circuitry. The controllercircuitry is configured to control the transceiver circuitry to receivean explicit uplink hybrid automatic repeat request acknowledgementindicator, e-HARQ indicator, from the infrastructure equipment, and todetermine, in accordance with the received e-HARQ indicator, whether ornot the communications device should monitor for a first HARQacknowledgement, HARQ-ACK, in a specific time slot and in a specificfrequency resource of the wireless access interface, the first HARQ-ACKbeing transmitted by the infrastructure equipment in response to anuplink transmission from the communications device to the infrastructureequipment.

Embodiments of the present technique, which further relate toinfrastructure equipment, methods of operating communications devicesand infrastructure equipment and circuitry for communications devicesand infrastructure equipment, allow for wireless communications networksto transmit an explicit uplink HARQ-ACK indicator to communicationsdevices, where the explicit uplink HARQ-ACK indicator is used to tellthe communications devices whether an explicit uplink HARQ-ACK should beexpected.

Respective aspects and features of the present disclosure are defined inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology. The described embodiments,together with further advantages, will be best understood by referenceto the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1a schematically represents some aspects of an LTE-type wirelesstelecommunication system which may be configured to operate inaccordance with certain embodiments of the present disclosure;

FIG. 1b schematically represents some aspects of a new radio accesstechnology (RAT) wireless telecommunications system which may beconfigured to operate in accordance with certain embodiments of thepresent disclosure;

FIG. 2 provides a schematic diagram of a structure of a downlink of awireless access interface of a mobile communications system operatingaccording to an LTE standard;

FIG. 3 provides a schematic diagram of an uplink of a wireless accessinterface of a mobile communications system operating according to anLTE standard;

FIG. 4 is a schematic block diagram of an example of a transmitter whichmay form part of a communications device (UE) or a base station (eNodeBor gNB) of the wireless communications network shown in FIG. 1a or FIG.1 b;

FIG. 5 is a schematic block diagram of an example of a receiver whichmay form part of a communications device (UE) or a base station (eNodeBor gNB) of the wireless communications network shown in FIG. 1a or FIG.1 b;

FIG. 6 illustrates an example of synchronous hybrid automatic repeatrequest (HARQ) operation for a physical uplink shared channel (PUSCH)with 8 HARQ processes;

FIG. 7 illustrates an example of a PUSCH HARQ time line;

FIG. 8 shows a part schematic, part message flow diagram representationof a communications system in accordance with embodiments of the presenttechnique;

FIG. 9 illustrates an example of an explicit HARQ (e-HARQ) indicatordependent on PUSCH HARQ process IDs in accordance with embodiments ofthe present technique;

FIG. 10 illustrates an example of time delays in a PUSCH transmission inaccordance with embodiments of the present technique; and

FIG. 11 illustrates an example of a time window comprising a pluralityof consecutive time slots used for conveying an explicit HARQ-ACK inaccordance with embodiments of the present technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Long Term Evolution Advanced Radio Access Technology (4G)

FIG. 1a provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 10 operatinggenerally in accordance with LTE principles, but which may also supportother radio access technologies, and which may be adapted to implementembodiments of the disclosure as described herein. Various elements ofFIG. 1a and certain aspects of their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP® body, and also described in many books on the subject, forexample, Holma H. and Toskala A [1]. It will be appreciated thatoperational aspects of the telecommunications networks discussed hereinwhich are not specifically described (for example in relation tospecific communication protocols and physical channels for communicatingbetween different elements) may be implemented in accordance with anyknown techniques, for example according to the relevant standards andknown proposed modifications and additions to the relevant standards.

The network 10 includes a plurality of base stations 11 connected to acore network 12. Each base station provides a coverage area 13 (i.e. acell) within which data can be communicated to and from terminal devices14. Data is transmitted from base stations 11 to terminal devices 14within their respective coverage areas 13 via a radio downlink (DL).Data is transmitted from terminal devices 14 to the base stations 11 viaa radio uplink (UL). The core network 12 routes data to and from theterminal devices 14 via the respective base stations 11 and providesfunctions such as authentication, mobility management, charging and soon. Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, communications device, andso forth. Base stations, which are an example of network infrastructureequipment/network access node, may also be referred to as transceiverstations/nodeBs/e-nodeBs/eNBs/g-nodeBs/gNBs and so forth. In this regarddifferent terminology is often associated with different generations ofwireless telecommunications systems for elements providing broadlycomparable functionality. However, certain embodiments of the disclosuremay be equally implemented in different generations of wirelesstelecommunications systems, and for simplicity certain terminology maybe used regardless of the underlying network architecture. That is tosay, the use of a specific term in relation to certain exampleimplementations is not intended to indicate these implementations arelimited to a certain generation of network that may be most associatedwith that particular terminology.

New Radio Access Technology (5G)

As mentioned above, the embodiments of the present invention can alsofind application with advanced wireless communications systems such asthose referred to as 5G or New Radio (NR) Access Technology. The usecases that are considered for NR include:

-   -   Enhanced Mobile Broadband (eMBB)    -   Massive Machine Type Communications (mMTC)    -   Ultra Reliable & Low Latency Communications (URLLC) [2]

eMBB services are characterised by high capacity with a requirement tosupport up to 20 Gb/s. The requirement for URLLC is a reliability of1-10⁻⁵ (99.999%) for one transmission of a 32 byte packet with a userplane latency of 1 ms [3].

The elements of the wireless access network shown in FIG. 1 a may beequally applied to a 5G new RAT configuration, except that a change interminology may be applied as mentioned above.

FIG. 1b is a schematic diagram illustrating a network architecture for anew RAT wireless mobile telecommunications network/system 30 based onpreviously proposed approaches which may also be adapted to providefunctionality in accordance with embodiments of the disclosure describedherein. The new RAT network 30 represented in FIG. 1b comprises a firstcommunication cell 20 and a second communication cell 21. Eachcommunication cell 20, 21, comprises a controlling node (centralisedunit) 26, 28 in communication with a core network component 31 over arespective wired or wireless link 36, 38. The respective controllingnodes 26, 28 are also each in communication with a plurality ofdistributed units (radio access nodes/remote transmission and receptionpoints (TRPs)) 22, 24 in their respective cells. Again, thesecommunications may be over respective wired or wireless links. Thedistributed units 22, 24 are responsible for providing the radio accessinterface for terminal devices connected to the network. Eachdistributed unit 22, 24 has a coverage area (radio access footprint) 32,34 which together define the coverage of the respective communicationcells 20, 21. Each distributed unit 22, 24 includes transceivercircuitry 22 a, 24 a for transmission and reception of wireless signalsand processor circuitry 22 b, 24 b configured to control the respectivedistributed units 22, 24.

In terms of broad top-level functionality, the core network component 31of the new RAT telecommunications system represented in FIG. 1b may bebroadly considered to correspond with the core network 12 represented inFIG. 1 a, and the respective controlling nodes 26, 28 and theirassociated distributed units/TRPs 22, 24 may be broadly considered toprovide functionality corresponding to base stations of FIG. 1 a. Theterm network infrastructure equipment/access node may be used toencompass these elements and more conventional base station typeelements of wireless telecommunications systems. Depending on theapplication at hand the responsibility for scheduling transmissionswhich are scheduled on the radio interface between the respectivedistributed units and the terminal devices may lie with the controllingnode/centralised unit and/or the distributed units/TRPs.

A terminal device 40 is represented in FIG. 1b within the coverage areaof the first communication cell 20. This terminal device 40 may thusexchange signalling with the first controlling node 26 in the firstcommunication cell via one of the distributed units 22 associated withthe first communication cell 20. In some cases communications for agiven terminal device are routed through only one of the distributedunits, but it will be appreciated in some other implementationscommunications associated with a given terminal device may be routedthrough more than one distributed unit, for example in a soft handoverscenario and other scenarios.

The particular distributed unit(s) through which a terminal device iscurrently connected through to the associated controlling node may bereferred to as active distributed units for the terminal device. Thusthe active subset of distributed units for a terminal device maycomprise one or more than one distributed unit (TRP). The controllingnode 26 is responsible for determining which of the distributed units 22spanning the first communication cell 20 is responsible for radiocommunications with the terminal device 40 at any given time (i.e. whichof the distributed units are currently active distributed units for theterminal device). Typically this will be based on measurements of radiochannel conditions between the terminal device 40 and respective ones ofthe distributed units 22. In this regard, it will be appreciated thesubset of the distributed units in a cell which are currently active fora terminal device will depend, at least in part, on the location of theterminal device within the cell (since this contributes significantly tothe radio channel conditions that exist between the terminal device andrespective ones of the distributed units).

In at least some implementations the involvement of the distributedunits in routing communications from the terminal device to acontrolling node (controlling unit) is transparent to the terminaldevice 40. That is to say, in some cases the terminal device may not beaware of which distributed unit is responsible for routingcommunications between the terminal device 40 and the controlling node26 of the communication cell 20 in which the terminal device iscurrently operating. In such cases, as far as the terminal device isconcerned, it simply transmits uplink data to the controlling node 26and receives downlink data from the controlling node 26 and the terminaldevice has no awareness of the involvement of the distributed units 22.However, in other embodiments, a terminal device may be aware of whichdistributed unit(s) are involved in its communications. Switching andscheduling of the one or more distributed units may be done at thenetwork controlling node based on measurements by the distributed unitsof the terminal device uplink signal or measurements taken by theterminal device and reported to the controlling node via one or moredistributed units.

In the example of FIG. 1 b, two communication cells 20, 21 and oneterminal device 40 are shown for simplicity, but it will of course beappreciated that in practice the system may comprise a larger number ofcommunication cells (each supported by a respective controlling node andplurality of distributed units) serving a larger number of terminaldevices.

It will further be appreciated that FIG. 1b represents merely oneexample of a proposed architecture for a new RAT telecommunicationssystem in which approaches in accordance with the principles describedherein may be adopted, and the functionality disclosed herein may alsobe applied in respect of wireless telecommunications systems havingdifferent architectures.

Thus certain embodiments of the disclosure as discussed herein may beimplemented in wireless telecommunication systems/networks according tovarious different architectures, such as the example architectures shownin FIGS. 1a and 1 b.

It will thus be appreciated the specific wireless telecommunicationsarchitecture in any given implementation is not of primary significanceto the principles described herein. In this regard, certain embodimentsof the disclosure may be described generally in the context ofcommunications between network infrastructure equipment/access nodes anda terminal device, wherein the specific nature of the networkinfrastructure equipment/access node and the terminal device will dependon the network infrastructure for the implementation at hand. Forexample, in some scenarios the network infrastructure equipment/accessnode may comprise a base station, such as an LTE-type base station 11 asshown in FIG. 1a which is adapted to provide functionality in accordancewith the principles described herein, and in other examples the networkinfrastructure equipment may comprise a control unit/controlling node26, 28 and/or a TRP 22, 24 of the kind shown in FIG. 1b which is adaptedto provide functionality in accordance with the principles describedherein.

LTE Wireless Access Interface

Those acquainted with LTE will appreciate that a wireless accessinterface configured in accordance with an LTE standard uses anorthogonal frequency division modulation (OFDM) based wireless accessinterface for the radio downlink (so-called OFDMA) and a single carrierfrequency division multiple access scheme (SC-FDMA) on the radio uplink.The down-link and the up-link of a wireless access interface accordingto an LTE standard is presented in FIGS. 2 and 3.

FIG. 2 provides a simplified schematic diagram of the structure of adownlink of a wireless access interface that may be provided by or inassociation with the base station of FIG. 1a when the communicationssystem is operating in accordance with the LTE standard. In LTE systemsthe wireless access interface of the downlink from an eNB to a UE isbased upon an orthogonal frequency division multiplexing (OFDM) accessradio interface.

In an OFDM interface the resources of the available bandwidth aredivided in frequency into a plurality of orthogonal subcarriers and datais transmitted in parallel on a plurality of orthogonal subcarriers,where bandwidths between 1.4 MHz and 20 MHz bandwidth may be dividedinto orthogonal subcarriers. Not all of these subcarriers are used totransmit data (some are used to carry reference information used forchannel estimation at the receiver for example) whilst some at the edgeof the band are not used at all. For LTE, the number of subcarriersvaries between 72 subcarriers (1.4 MHz) and 1200 subcarriers (20 MHz),but it will be appreciated that for other wireless access interfaces,such as NR or 5G, the number of sub-carriers and the bandwidth may bedifferent. Each subcarrier bandwidth may take any value but in LTE it isfixed at 15 kHz.

As shown in FIG. 2, the resources of the wireless access interface arealso temporally divided into frames where a frame 200 lasts 10 ms and issubdivided into 10 sub-frames 201 each with a duration of 1 ms. Eachsub-frame 201 is formed from 14 OFDM symbols and is divided into twoslots 220, 222 each of which comprise six or seven OFDM symbolsdepending on whether a normal or extended cyclic prefix is beingutilised within OFDM symbols for the reduction of inter symbolinterference. The resources within a slot may be divided into resourcesblocks 203 each comprising 12 subcarriers for the duration of one slotand the resource blocks are further divided into resource elements 204which span one subcarrier for one OFDM symbol, where each rectangle 204represents a resource element. The resource elements distributed in timewithin a sub-frame and frequency across the host system bandwidthrepresent the communications resources of the host system.

The simplified structure of the downlink of an LTE wireless accessinterface presented in FIG. 2, also includes an illustration of eachsub-frame 201, which comprises a control region 205 for the transmissionof control data, a data region 206 for the transmission of user data andreference signals 207 which are interspersed in the control and dataregions in accordance with a predetermined pattern. The control region205 may contain a number of physical channels for the transmission ofcontrol data, such as a physical downlink control channel (PDCCH), aphysical control format indicator channel (PCFICH) and a physical HARQindicator channel (PHICH). The data region may contain a number ofphysical channels for the transmission of data or control, such as aphysical downlink shared channel (PDSCH), enhanced physical downlinkcontrol channel (ePDCCH) and a physical broadcast channel (PBCH).Although these physical channels provide a wide range of functionalityto LTE systems, in terms of resource allocation and the presentdisclosure, ePDCCH and PDSCH are most relevant.

Resources within the PDSCH may be allocated by an eNodeB to UEs beingserved by the eNodeB. For example, a number of resource blocks of thePDSCH may be allocated to a UE in order that it may receive data that ithad previously requested or data which is being pushed to it by theeNodeB, such as radio resource control (RRC) signalling. In FIG. 2, UE1has been allocated resources 208 of the data region 206, UE2 resources209 and UE3 resources 210. UEs in an LTE system may be allocated afraction of the available resources for the PDSCH and therefore UEs arerequired to be informed of the location of their allocated resourceswithin the PDCSH so that only relevant data within the PDSCH is detectedand estimated. In order to inform the UEs of the location of theirallocated communications resource elements, resource control informationspecifying downlink resource allocations is conveyed across the PDCCH ina form termed downlink control information (DCI), where resourceallocations for a PDSCH are communicated in a preceding PDCCH instancein the same sub-frame.

FIG. 3 provides a simplified schematic diagram of the structure of anuplink of an LTE wireless access interface that may be provided by or inassociation with the eNodeB of FIG. 1 a. In LTE networks the uplinkwireless access interface is based upon a single carrier frequencydivision multiplexing FDM (SC-FDM) interface and downlink and uplinkwireless access interfaces may be provided by frequency divisionduplexing (FDD) or time division duplexing (TDD), where in TDDimplementations sub-frames switch between uplink and downlink sub-framesin accordance with predefined patterns. However, regardless of the formof duplexing used, a common uplink frame structure is utilised. Thesimplified structure of FIG. 3 illustrates such an uplink frame in anFDD implementation. A frame 300 is divided into 10 sub-frames 301 of 1ms duration where each sub-frame 301 comprises two slots 302 of 0.5 msduration. Each slot is then formed from seven OFDM symbols 303 where acyclic prefix 304 is inserted between each symbol in a manner equivalentto that in downlink sub-frames.

Physical Layer Transmission and Reception

Embodiments of the present technique can find application in atransmitter and receiver which employs an OFDM-based waveform totransmit and receive data. Examples of OFDM-based waveforms include theLTE downlink and the LTE uplink, where the LTE uplink uses a DiscreteFourier Transform spread OFDM (DFT-S-OFDM) waveform. The LTE uplinkhence implements an OFDM-based Single Carrier Frequency DivisionMultiple Access scheme (SC-FDMA). References to “OFDM” in the currentdescription hence also apply to an SC-FDMA based waveform, as will beunderstood by a skilled artisan. As such, embodiments of the presenttechnique can find application in a UE and an eNB of a wirelesscommunications system, which may conform to an NR/5G standard or an LTEstandard. An arrangement of signal processing blocks, which may beimplemented as integrated circuits or processing units, which may beused to form part of physical layer processing in transmitters andreceivers of a wireless communication systems such as those of FIGS. 1aand 1b are illustrated in FIGS. 4 and 5. FIGS. 4 and 5 will now bedescribed in order to gain a better appreciation of the embodimentsdescribed in the following paragraphs.

As shown in FIG. 4 a data source 320 feeds data to be transmitted viathe wireless access interface in for example the eNB or gNB to anautomatic repeat request (ARQ) controller 322. The ARQ controller 322forms the data from the data source 320 into data units for transmissionin one or more subframes of the wireless access interface. The ARQcontroller 322 may operate to control transmission of data in accordancewith various types of ARQ processes known to those skilled in the art.Such techniques typically involve forming the data to be transmittedinto data units, transport blocks or data packets for transmission. TheARQ controller 322 may operate in combination with a data encoder 324 toencode data packets to determine whether they have been correctlyreceived and to improve the likelihood that the data packets arereceived correctly. In accordance with an ARQ protocol performed by theARQ controller 322, a receiver may transmit a feedback signalrepresenting either acknowledgement ACK, or a negative acknowledgmentNACK in dependence upon whether a data packet has been successfullyreceived or not received successfully. In response to detecting an NACKor not detecting an ACK, the ARQ controller 322 may respond byretransmitting the data unit which was not received correctly. In someexamples, the ARQ controller may transmit increasing amounts ofredundant data generated by the data encoder 324 in response to anindication that a data packet cannot be decoded. However there are manyvariations on ARQ protocols and the present technique is not limited toa particular protocol.

The data encoder 324 receives each data unit and performs encoding andscrambling to improve the integrity of the transmitted data and toprovide some rejection of co-channel interference. The encoded data isthen received at a modulator 326, which maps the data onto modulationsymbols and performs other processing tasks to convert the modulationsymbols into modulation cells. The modulation cells generated by themodulator 326 are then received by a resource element mapper 328 whichmaps the modulation cells onto the subcarriers of OFDM symbols which incombination with the OFDM symbol builder 328 generates OFDM symbols. TheOFDM symbols are then used to modulate a radio frequency carrier fortransmission by an RF modulator 332 from the antenna 334.

As shown in FIG. 5 at the receiver a radio frequency detector may detectthe transmitted signal (from the base station or UE as appropriate)using a radio frequency detector 340. The radio frequency detector 340may in some configurations include a plurality of antennas 342, 344which may provide a multiple input multiple output (MIMO) or singleinput, multiple output diversity scheme. An OFDM symbol detector 346then receives a baseband version of the signal detected by the radiofrequency detector and recovers the OFDM symbols. The OFDM symboldetector includes a forward Fast Fourier Transform (FFT) whichtransforms the time domain signal into the frequency domain. The OFDMsymbols are then fed to a demodulator 348, which demodulates thesubcarriers to generate for each sub-carrier a received modulation cell,which is then mapped back into the data symbols to reverse operationsperformed by the modulator. The received data is then fed to the datadecoder 350 which performs error correction decoding, descrambling anderror detection decoding (for example using a CRC check, which is usedto generate the ACKINACK) to reverse the operations performed at thetransmitter by the data encoder 324 in order to improve the integrity ofthe received data and co-operates with an ARQ controller 352 in thereceiver to determine whether data packets transmitted by thetransmitter can be correctly received. The ARQ controller 352 thereforegenerates the ACKINACK responses for transmission to the transmitter,using a receiver-transmitter 356 included in the entity with thereceiver of FIG. 5 to organise the re-transmissions as appropriate. TheARQ controller 352 then reassembles the data units into the data aspresented by for example a higher layer application which is forwardedto a data sink.

As shown in FIG. 5 the demodulator 348 includes an equaliser 360, achannel estimator 362 and an OFDM demodulation unit 364. The channelestimator 362 receives the detected OFDM symbol from the OFDM symboldetector 346 and generates an estimate of an impulse response of thechannel through which the received OFDM symbol has passed. The impulseresponse may be generated in the frequency domain as a set of estimatedphase and amplitude distortions across the frequency domain. To thisend, according to a conventional arrangement, the received OFDM symbolincludes reference symbols which transmit known symbols which whencorrelated with a reproduction of those symbols are used to generate anestimate of the impulse response of the channel. The channel estimate istherefore fed to the equaliser 360, which compensates for thedistortions caused by the channel, from the received modulation symbols.The OFDM demodulation unit then demodulates the OFDM symbol to providelog-likelihood ratios (LLRs) on the bits associated with the modulationssymbols. The LLRs are an example of soft decision bits. As will beappreciated there are other ways of performing equalisation of thereceived signal which can be done in the frequency domain or the timedomain and therefore the equaliser 360 may form part of the OFDMdemodulation unit 364. However the architecture showing in FIG. 5 hasbeen provided in order to illustrate an example embodiment to thepresent technique which will be explained shortly.

The example transmitter and receiver shown in FIGS. 4 and 5 areconfigured to transmit data using an ARQ process according to aconventional arrangement of a transmitter and receiver chain.Embodiments of the present technique can provide an arrangement in whichthe reliability of data communicated by such an example transmitter andreceiver chain incorporating an ARQ process can be improved, with an ARQtechnique which relies on repeated transmission of data units or packetsuntil that data unit or packet can be successfully decoded. As suchembodiments of the present technique can find application with URLLCdevices, such as those which find application with LTE or 5G new radio(NR).

Embodiments of the present technique can therefore provide animprovement to communications services, which deliver data with arelatively high reliability and with a relatively low latency. Suchcommunications services therefore present a significant challenge whencommunicating via wireless access interfaces in which the radiocommunications conditions vary and the communications devicetransmitting or receiving the data may be mobile. In one example thecommunications may provide an ultra reliable low latency communications(URLLC) service, such as that being proposed within 3GPP for 4G and 5Gcommunications networks. In some examples, URLLC communications areeither low latency (where the user plane latency target is 1 ms) or highreliability (where the acceptable error rate on URLLC transmissions is10⁻⁵) or both low latency and high reliability (where both the latencyand reliability targets need to be met at the same time).

Various techniques have been proposed in order to achieve the lowlatency and high reliability targets. Low latency can be achievedthrough one or more of the following techniques (which can be applied incombination):

-   -   Short scheduling interval. Transmissions can be scheduled at        frequent intervals. The scheduling interval may be less than the        duration of a slot in the frame (e.g. when the slot duration is        1 ms, it may be possible to schedule URLLC every 0.1 ms, i.e.        with a scheduling interval of 0.1 ms).    -   Short TTI. The transmission time interval (TTI) of a URLLC        transmission may consist of a small number of OFDM symbols (i.e.        much smaller than the duration of a slot).    -   On the fly decoding format. The format of the URLLC transmission        may be designed to allow for “on the fly decoding”. For example,        reference symbols for channel estimation purposes may be located        in the first OFDM symbol of the URLLC transmission and each OFDM        symbol within the URLLC transmission can be decoded        independently of other OFDM symbols (e.g. one OFDM symbol        contains a whole forward error correction (FEC) codeword).

The short TTI referred to above can be termed a “mini-slot”. Thescheduling interval may also have an extent of a mini-slot.

High reliability can be achieved through one or more of the followingtechniques (which can be applied in combination):

-   -   Frequency diverse transmissions: Transmission of the URLLC        information over a wide bandwidth makes those transmissions        resilient to frequency selective fading.    -   Antenna diversity: Antenna diversity makes the URLLC        transmission resilient to frequency selective fading on some of        the channels between transmit and receive antennas.    -   Robust coding and modulation: Use of powerful forward error        correction codes and robust modulation formats increases the        resilience of the URLLC transmission to noise.    -   Hybrid ARQ: The URLLC transmission is protected with a cyclic        redundancy check (CRC). If the CRC indicates that the URLLC        packet is incorrect, the receiver can inform the transmitter of        the error and the packet can be re-transmitted.    -   Repetition: The URLLC transmission can be repeated, such that if        an initial reception of the packet fails, a second reception of        the packet can be combined with the first reception of the        packet to increase the effective signal to noise ratio (SNR) of        the received packet and allow decoding of the packet.

HARQ Transmission in LTE

In LTE, synchronous Hybrid ARQ (HARQ) transmission is supported forPUSCH (uplink) transmission where the HARQ process ID is linked to thesubframe, that is, the eNB and UE know which HARQ process is beingaddressed based on the subframe being processed. In LTE for FDD, thereare 8 HARQ processes as shown in FIG. 6 and the HARQ process IDincreases in order, for example, if at subframe n 60 the HARQ process IDis 0, then in subframe n+1 62 the HARQ process ID is 1 and so on and theHARQ process ID reverts back to 0 after the 8^(th) HARQ process 64, i.e.with ID 7.

For PUSCH transmission in LTE, the delay between the PUSCH transmissionand the uplink grant and the delay between the uplink HARQ feedback(HARQ-ACK) and the PUSCH transmission are fixed to 4 subframes (i.e. 4ms). Hence the eNB and UE know when a PUSCH transmission for a specificHARQ process ID is transmitted over the air and when the correspondingHARQ-ACK is expected, without any signalling for the time resource andHARQ process ID. An example is shown in FIG. 7, where the eNB 70transmits a PDCCH (or EPDCCH) carrying a DCI with an uplink grant 74(containing scheduled resources for PUSCH) for a UE 72 at time t₁, whichis received at the UE 72 at time t₂ after propagation delay. The timeresource, e.g. subframe, for the transmission of the PUSCH 76 is notindicated in the uplink grant 74 but is known to occur four subframeslater after the uplink grant 74 at time t₃, which is received by the eNB70 at time t₄. Note that due to timing advance the PUSCH is transmitted76 in advance to account for propagation delay between the eNB 70 and UE72. The UE 72 would then expect an uplink HARQ-ACK 78 from the eNB 70four subframes later at time t₆.

The type of uplink HARQ-ACK can be adaptive or non-adaptive. In anadaptive HARQ system, the uplink HARQ-ACK is an uplink grant in a DCIcarried by a PDCCH (or EPDCCH). Here the DCI will indicate whether thisuplink grant is for a new Transport Block (TB) or whether it is aretransmission and it can schedule a different resource (e.g. frequencyresource) for the retransmission. LTE also uses non-adaptive HARQ and inLTE, the uplink HARQ-ACK is carried by PHICH (Physical Hybrid-ARQIndicator Channel) which has 1 bit of information to indicate an ACK(i.e. the PUSCH TB is received successfully) or a NACK (i.e. failed toreceive the PUSCH TB). The PHICH does not signal the resource for thePUSCH retransmission but a NACK would implicitly indicate that the sameresource used for the previous PUSCH transmission will be scheduled forthe PUSCH retransmission.

HARQ Transmission in NR

In NR, an asynchronous HARQ is used for PUSCH transmission, where unlikeLTE, there is no fixed association between the subframe and the HARQprocess ID. This allows the time resource (i.e. the slot) for PUSCHtransmission to be flexible, that is, the time resource (i.e. slot) andHARQ process ID for PUSCH transmission are indicated in the uplinkgrant.

Unlike LTE where an explicit uplink HARQ-ACK is provided by the eNB at aknown time (i.e. 4 subframes after PUSCH transmission), in NR animplicit HARQ-ACK is provided. That is a PUSCH TB of a HARQ process isACKed (positively acknowledged) if an uplink grant indicates a new PUSCHTB is scheduled (toggling the New Data Indicator bit, potentially theNDI functionality is provided by “Code Block Group Indicator” bits) forthe same HARQ process. The PUSCH TB of a HARQ process is NACKed(negatively acknowledged) if an uplink grant does not indicate a newPUSCH TB is scheduled for the same HARQ process and here the resourcesscheduled are used for retransmission of the PUSCH TB. Therefore unlikeLTE, the UE does not know when or whether any uplink HARQ-ACK istransmitted. It should be noted that there may not be any uplinkHARQ-ACK feedback at all if there is no new data transmission.

As described above, for URLLC the PUSCH TB needs to have highreliability and low latency. Since in NR the UE does not know when theuplink HARQ-ACK is expected, it is difficult for the UE to determinewhether its uplink URLLC transmission is successfully received. Thistherefore has an impact on the reliability requirement of URLLC.Recognising this, 3GPP proposed to introduce explicit HARQ-ACK for URLLCtransmission.

It should be appreciated that the 3GPP NR specifications do notdistinguish a PUSCH transmission as URLLC or eMBB but from the layer 1point of view, it is merely data transmission (i.e. layer 1 is agnosticas to whether the transmission is URLLC or eMBB). Hence, theintroduction of explicit HARQ-ACK targeting URLLC transmissions imposesa challenge since layer 1 does not distinguish whether the transmissionis for URLLC or eMBB.

Explicit Uplink HARQ-ACK Indicator for URLLC

Embodiments of the present technique allow for wireless communicationsnetworks network to transmit an explicit uplink HARQ-ACK indicator tocommunications devices, where the explicit uplink HARQ-ACK indicator isused to tell the communications devices whether an explicit uplinkHARQ-ACK should be expected.

FIG. 8 shows a part schematic, part message flow diagram representationof a communications system 80 in accordance with embodiments of thepresent technique. The communications system 80 comprises aninfrastructure equipment 81 and a communications device 82. Each of theinfrastructure equipment 81 and communications device 82 comprise atransceiver (or transceiver circuitry) 81.1, 82.1, and a controller (orcontroller circuitry) 82.1, 82.2. Each of the controllers 82.1, 82.2 maybe, for example, a microprocessor, a CPU, or a dedicated chipset, etc.It will be appreciated by those skilled in the art that, in arrangementsof the present technique, the transceiver 82.1 of the communicationsdevice 82 may not always include a transmitter, for example in scenarioswhere the communications device 82 is a low-power wearable device.

As shown in FIG. 8, the communications device 82 is configured toreceive 84 an explicit uplink hybrid automatic repeat requestacknowledgement indicator, e-HARQ indicator, from the infrastructureequipment 81, and to determine 86, in accordance with the receivede-I-IARQ indicator 84, whether or not the communications device 82should monitor for a first HARQ acknowledgement 88, HARQ-ACK, in aspecific time slot 88.1 and in a specific frequency resource 88.2 of thewireless access interface, the first HARQ-ACK 88 being transmitted bythe infrastructure equipment 81 in response to an uplink transmission 89from the communications device to the infrastructure equipment 81.

Essentially, embodiments of the present technique introduce an explicituplink HARQ-ACK Indicator (e-HARQ Indicator). The e-HARQ Indicatorindicates whether the UE should decode the uplink HARQ-ACK in anexplicit manner (e.g. using a PHICH-like channel, as per LTE) or whetherit should decode the uplink HARQ-ACK in an implicit manner. By having anindicator to tell the UE to monitor for an explicit uplink HARQ-ACK,there is no need to distinguish whether a PUSCH transmission is forURLLC or eMBB. An indicator will also avoid the UE having to blindlywait for a possible acknowledgement from the gNB: instead, the UE willdecode for an explicit HARQ-ACK at a known time and frequency resource.The reduction in blind decoding reduces the rate at which the UEincorrectly decodes the uplink HARQ-ACK (each blind decoding operationallows the potential for an incorrect decoding event).

It should be noted that an explicit uplink HARQ-ACK indicator istransmitted in the downlink and informs the UE whether a future uplinkHARQ-ACK (transmitted in the downlink) will be transmitted explicitly orimplicitly.

In an arrangement, the said e-HARQ Indicator is transmitted in the DCIwhere the UE is the recipient or one of the recipients. That is, whetherthe UE needs to monitor for an explicit HARQ-ACK at a known time andfrequency resource is dynamically indicated. This gives the gNBflexibility on which PUSCH transmission to provide an explicit HARQ-ACK.In other words, the controller circuitry is configured to control thetransceiver circuitry to receive, as downlink control information, DCI,from the infrastructure equipment, an uplink grant indicating resourcesof the wireless access interface that the communications device shoulduse for the uplink transmission to the infrastructure equipment, whereinthe uplink grant comprises the e-HARQ indicator. This DCI can carry anuplink grant which is specific to the UE or it can be a group common DCIcarrying, for example the Slot Format Indicator (SFI). In anotherexample, the Slot Format Indicator which informs a group of UEs on thestructure of at least one slot also carries the e-HARQ Indicator. Inother words, the controller circuitry is configured to control thetransceiver circuitry to receive, as group common DCI from theinfrastructure equipment, a Slot Format Indicator indicating aconfiguration of one or more time divided slots of a wireless accessinterface provided by the wireless communications network fortransmitting data to the communications device on the downlink orreceiving data from the communications device on the uplink, wherein theSlot Format Indicator comprises the e-HARQ indicator.

In another arrangement, the said e-HARQ Indicator is configured by theRRC. That is, the e-HARQ Indicator is semi-statically configured andonce configured the UE will expect an explicit uplink HARQ-ACK for itsPUSCH transmissions. In other words, the controller circuitry isconfigured to control the transceiver circuitry to receive a radioresource control, RRC, configuration message from the wirelesscommunications network, the RRC configuration message comprising thee-HARQ indicator.

In another arrangement, the said e-HARQ Indicator RRC configurationincludes criteria based on the parameters set in the DCI in which the UEis the recipient or one of the recipients, for example an uplink grantor a group common DCI. That is explicit HARQ-ACK is enabled if the saidcriteria are met in the uplink grant or the DCI where the UE is arecipient. Since the uplink grant is dynamic, this enables the gNB todynamically set the explicit HARQ-ACK for a PUSCH transmission. That isto say, the values set in the uplink grant implicitly indicate whetherthe UE should monitor for an explicit HARQ-ACK. In other words, thecontroller circuitry is configured to control the transceiver circuitryto receive, from the infrastructure equipment, an uplink grantindicating resources of the wireless access interface that thecommunications device should use for the uplink transmission to theinfrastructure equipment, wherein the received e-HARQ indicator isdependent on at least one parameter of the received uplink grant.

In a first example of this arrangement, the said criterion in the RRCconfigured e-HARQ Indicator is the HARQ process ID. Each HARQ process IDhas a corresponding e-HARQ Indicator telling the UE whether to expect anexplicit HARQ-ACK. Since the HARQ process ID is indicated in the uplinkgrant carried by the DCI, by selecting the HARQ process ID the gNB wouldimplicitly also tell the UE whether it will feedback an explicitHARQ-ACK. That is the gNB can dynamically decide whether to transmit anexplicit HARQ-ACK by setting the HARQ process ID in the uplink grant. Inother words, the at least one parameter of the received uplink grant isan identifier of a HARQ process used by the infrastructure equipment totransmit a HARQ-ACK to the communications device in response to theuplink transmission.

An example is shown in FIG. 9, where the maximum number of HARQ processis configured to be 8 (it should be noted that, in NR, the number ofHARQ process is configurable) and an explicit HARQ is configured forHARQ process ID #0, #4 and #5. When there are uplink grants for theseHARQ processes={0, 4, 5} the UE monitors for explicit HARQ-ACK at aknown time and in a known frequency resource, while for other HARQprocesses {1, 2, 3, 6, 7}, the UE does not monitor for explicit HARQ-ACKat all, but instead monitors for an implicit HARQ-ACK in the form of anuplink grant as described above.

In another example of this arrangement, the said criterion in the RRCconfigured e-HARQ Indicator is the time delay T_(DCI-PUSCH) between theuplink grant and the PUSCH transmission (it should be noted thatcurrently, this time delay is signalled in the uplink grant). That is,if T_(DCI-PUSCH) is less than a threshold T_(URLLC) then the e-HARQIndicator is enabled, or otherwise it is disabled. The value T_(URLLC)can be RRC configured or specified in the specifications. This examplerecognises that the URLLC packet has low latency and would thereforerequire a short T_(DCI-PUSCH) value. Hence, for these PUSCHtransmissions, the UE would expect an explicit HARQ-ARQ at known timeand frequency resource. In other words, the at least one parameter ofthe received uplink grant is a time delay between the transmission ofthe uplink grant by the infrastructure equipment and the transmission ofthe uplink transmission by the communications device.

In another example of this arrangement, the said criterion in the RRCconfigured e-HARQ Indicator is the PUSCH Transport Block Size (TBS)scheduled by the uplink grant. An example implementation may be thatexplicit HARQ-ACK is enabled if the TBS is less than a predefinedthreshold. This threshold can be RRC configured or can be specified inthe specifications. This example recognises that URLLC transmissiontypically consists of small packets; as described in [3] the expectedURLLC packet is 32 bytes. The UE would therefore monitor for explicitHARQ-ACK if the scheduled PUSCH TBS is less than the predeterminedthreshold. In other words, the at least one parameter of the receiveduplink grant is a transport block size, TBS, scheduled by the uplinkgrant.

Alternatively, RRC configures explicit feedback for a logical channel.So, when data related to that particular logical channel is included inthe TB, the UE expects an explicit feedback. In an arrangement, the UEonly sends an ACK via the explicit HARQ-ACK. This particularlyapplicable for cases where the logical channel ID can only be accuratelydetermined when the TB is successfully decoded. In an arrangement, anexplicit HARQ-ACK is used if the previous scheduling request or bufferstatus report (sent by the UE to the base station) that was sentindicated that the UE had data to transmit for a logical channel towhich explicit HARQ-ACK applied.

In another example of this arrangement, the said criterion in the RRCconfigured e-HARQ Indicator is a monitoring granularity of PDCCH for theuplink grant. The granularity is configured via RRC for a resource setfor PDCCH. An example implementation is that explicit HARQ-ACK isenabled if the granularity is less/more than a predefined threshold. Anexample of the predefined threshold is a time length of a subframe, i.e.1 ms. In another example, the predefined threshold is determined basedon a subcarrier spacing used for the PDCCH. The granularity may be basedon TTI (Transmission Time Interval). In other words, the at least oneparameter of the received uplink grant is a granularity used by thecommunications device to monitor the wireless access interface for theuplink grant from the infrastructure equipment. The granularity may bedetermined in accordance with a transmission time interval, TTI, of thewireless communications network.

In another arrangement, the said criterion in the RRC configured e-HARQIndicator is a slot format which may be determined for each symbol basedon UE-specific DCI, a Slot Format Indicator (SFI) indicated byGroup-Common PDCCH which may be transmitted for a UE group and/or a SFIconfigured by RRC signaling. The SFI indicates a slot format (e.g.downlink, uplink or flexible) for each symbol in one or more subframes.The Group-Common PDCCH is different from PDCCH for the uplink grant. AUE assumes downlink transmissions to occur in ‘downlink’ or ‘flexible’symbols only. A UE transmits in ‘uplink’ or ‘flexible’ symbols only. Anexample implementation is that explicit HARQ-ACK is enabled if the SFIor the slot format indicates a predefined slot format. In other words,the controller circuitry is configured to control the transceivercircuitry to receive, from the infrastructure equipment, an SFI, the SFIindicating a configuration of one or more time divided slots of awireless access interface provided by the wireless communicationsnetwork for transmitting data to the communications device on thedownlink or receiving data from the communications device on the uplink,wherein the SFI is provided by one of the RRC configuration message, anSFI communicated in a group communications channel and DCI, and whereinthe received e-HARQ indicator is dependent on at least one parameter ofthe received SFI. In an example of this arrangement, the at least oneparameter of the received SFI is the configuration of the one or moretime divided slots of the wireless access interface.

It would be appreciated by those skilled in the art that the variouscriteria discussed in the arrangements above may be implemented togetheror individually.

In an arrangement, the UE will decode an explicit uplink HARQ-ACK, undercontrol of the e-HARQ Indicator, only if the UE hasn't previouslyreceived an implicit HARQ-ACK for that transport block. This can beuseful for UE power saving. If the gNB schedules the UE with a finalPUSCH transmission (i.e. when the UE buffer status is known to be at, orclose to, zero), it can set the e-HARQ Indicator to indicate to the UEthat it should look for an explicit uplink HARQ ACK/NACK (after which itcan potentially go to sleep). However, if the PUSCH transmission isreceived in error by the gNB, the gNB can send an implicit uplinkHARQ-NACK to the UE, causing the UE to re-transmit the PUSCH. In such anarrangement, the explicit uplink HARQ-ACK would typically be configuredto occur at a relatively longer time after the PUSCH transmission. Inother words, the controller circuitry is configured to control thetransceiver circuitry to determine whether or not the communicationsdevice has received a second HARQ-ACK from the infrastructure equipmentin response to the uplink transmission, and to monitor for the firstHARQ-ACK in the specific time slot and in the specific frequencyresource of the wireless access interface in accordance with thereceived e-HARQ indicator only if the communications device has notreceived the second HARQ-ACK.

Time Resource for Explicit HARQ-ACK

In another arrangement, the said known time resources where the UEmonitors for an explicit HARQ-ACK is fixed in the specifications. Thistime resource can be referenced as the delay between the end of PUSCHtransmission and start of the explicit uplink HARQ-ACK as shown asT_(HARQ) in FIG. 10. Since the URLLC transmission is low latency, theHARQ-ACK should therefore reach the UE as soon as possible, for examplein the next slot after the PUSCH transmission (i.e. the value ofT_(HARQ) may typically be 1 slot). In other words, the specific timeslot in which the communications device should monitor for the firstHARQ-ACK is predetermined and is known to the communications device.

In another arrangement, the said know time resource, i.e. T_(HARQ),where the UE monitors for an explicit HARQ-ACK is configured by RRC. Inother words, the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK is indicated in an RRCconfiguration message received by the communications device from theinfrastructure equipment.

In another arrangement, the said known time resource, i.e. T_(HARQ),where the UE monitors for an explicit HARQ-ACK is indicated in theuplink grant scheduling the PUSCH transmission. That is, the timeresource is dynamically scheduled by the gNB. In other words, thecontroller circuitry is configured to control the transceiver circuitryto receive, from the infrastructure equipment, an uplink grantindicating resources of the wireless access interface that thecommunications device should use for the uplink transmission to theinfrastructure equipment, wherein the specific time slot in which thecommunications device should monitor for the first HARQ-ACK is indicatedin the uplink grant.

In another arrangement, the said known time resource, i.e. T_(HARQ),where the UE monitors for an explicit HARQ-ACK is implicitly indicatedby the time delay T_(DCI-PUSCH) between the uplink grant and the PUSCHtransmission. That is, the UE would derive T_(HARQ) from T_(DCI-PUSCH)using a known function in the specifications. An example is thatT_(HARQ) is proportional to T_(TDI-PUSCH). That is, when T_(DCI-PUSCH)increases, T_(HARQ) increases. It should be appreciated that this is anexample function and other functions are possible. In other words, thecontroller circuitry is configured to control the transceiver circuitryto determine the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK in accordance with a time delaybetween the transmission of the uplink grant by the infrastructureequipment and the transmission of the uplink transmission by thecommunications device

In another arrangement, the said time resource where the UE monitors foran explicit HARQ-ACK consists of a time window W_(HARQ) of N consecutiveslots where the explicit HARQ-ACK can be transmitted in one or more ofthese N consecutive slots. The value N can be specified in thespecifications or configured by RRC. The UE would therefore monitor thistime window and decode each slot for possible explicit HARQ-ACK. Inother words, the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK is one of a plurality ofconsecutive time slots forming a time window, and the communicationsdevice is configured to monitor one or more of the plurality ofconsecutive time slots of the time window for the first HARQ-ACK.

This arrangement provides flexibility for the gNB to schedule theexplicit HARQ-ARQ and also allows for the explicit HARQ-ACK to berepeated for higher reliability. An example is shown in FIG. 11, wherethe time window W_(HARQ) consists of N=4 slots that starts at time t₄and ends at time t₈. The UE monitors these N=4 slots for explicitHARQ-ACK and here the explicit HARQ-ACK is repeated twice between timet₅ and t₇.

Frequency Resource for Explicit HARQ-ACK

In another arrangement, the said frequency resources where the UEmonitors for an explicit HARQ-ACK is RRC configured. In other words, thespecific frequency resource in which the communications device shouldmonitor for the first HARQ-ACK is indicated in an RRC configurationmessage received by the communications device from the infrastructureequipment.

In another arrangement, the said RRC configured frequency resourcecarries a PHICH. Here, a non-adaptive HARQ is used where the PHICHcarries a single bit indicating an ACK or a NACK. In other words, thespecific frequency resource in which the communications device shouldmonitor for the first HARQ-ACK contains a physical hybrid ARQ indicatorchannel, PHICH, wherein the PHICH comprises a single bit indicating apositive acknowledgement or a negative acknowledgement. Hence, thee-HARQ indicator acts as a switch to enable or disable PHICH for aparticular UE.

In another arrangement, the said RRC configured frequency resourcecarries an uplink grant, i.e. the explicit HARQ-ACK is an adaptive HARQ.That is the frequency resource is a PDCCH search space where the UEmonitors for an explicit uplink HARQ-ACK in the form of an uplink grant.In other words, the specific frequency resource in which thecommunications device should monitor for the first HARQ-ACK contains anuplink grant indicating resources of the wireless access interface thatthe communications device should use for the uplink transmission to theinfrastructure equipment.

In another arrangement the UE monitors the time and frequency resourcescarrying the PHICH (non-adaptive HARQ) and also for uplink grant(adaptive HARQ). This arrangement has the benefit that the reliabilityis increased when both the PHICH and uplink grant transmit the explicitHARQ-ACK. Of course, the gNB can also use one of these resources for thetransmission of the explicit HARQ-ACK where the UE would reduce itsoverhead if the scheduled resources for retransmission is the same anduses PHICH and if the gNB wishes to change the retransmission resourcesit can use an uplink grant. In other words, the controller circuitry isconfigured to control the transceiver circuitry to monitor for the firstHARQ acknowledgement, HARQ-ACK, in a first specific time slot and in afirst specific frequency resource of the wireless access interface, andto monitor for the first HARQ acknowledgement, HARQ-ACK, in a secondspecific time slot and in a second specific frequency resource of thewireless access interface, wherein the first specific frequency resourcecontains a PHICH comprising a single bit indicating a positiveacknowledgement or a negative acknowledgement, and wherein the secondspecific frequency contains an uplink grant indicating resources of thewireless access interface that the communications device should use forthe uplink transmission to the infrastructure equipment.

In an arrangement, there is more than one frequency resource where theUE monitors for an explicit HARQ-ACK. For example, the gNB can configurethe UE to monitor ‘N’ frequency resources for the explicit HARQ-ACK. Inother words, the specific frequency resource in which the communicationsdevice should monitor for the first HARQ-ACK is one of a plurality offrequency resources, and the communications device is configured tomonitor each of the plurality of frequency resources for the firstHARQ-ACK. In such an arrangement, the following functionalities arepossible:

-   -   UE monitors all ‘N’ frequency resources and if at least one        resource indicates NACK, the UE re-transmits the PUSCH. This        increases PUSCH reliability and reduces latency for URLLC use        cases (if it is not certain that a PUSCH has been received by        the gNB, the UE re-transmits the PUSCH). In other words, if one        or more of the plurality of frequency resources comprise a        negative acknowledgement, the communications device is        configured to re-transmit the uplink transmission to the        infrastructure equipment.    -   UE monitors all ‘N’ frequency resources and if all the resources        indicate ACK, the UE flushes the UL transmit data from its        buffers. This increases PUSCH reliability for URLLC use cases        (the UE only flushes its uplink transmit buffers if it is sure        that the uplink data has been received by the gNodeB and there        will not be a future request to re-transmit that uplink data).        In other words, if all of the plurality of frequency resources        comprise a positive acknowledgement, the communications device        is configured to clear the data transmitted as the uplink        transmission from a buffer of the communications device.    -   The UE performs soft combining on the ‘N’ frequency resources.        This provides frequency diversity for the uplink HARQ-ACK        feedback channel.

It would be appreciated by those skilled in the art that the timeresource for PHICH and the uplink grant carrying the explicit HARQ-ACKneed not be the same.

Grant-Free Transmission

A PUSCH can be transmitted using grant-free uplink resources where a setof uplink resources is configured for the UE to use without an explicituplink grant from the gNB. In other words, the controller circuitry isconfigured to control the transceiver circuitry to determine that thecommunications device has been assigned grant-free resources of thewireless access interface by the infrastructure equipment, to determine,without reception of an uplink grant from the infrastructure equipment,resources of the grant-free resources of the wireless access interfacethat the communications device should use for the uplink transmission tothe infrastructure equipment, and to transmit the uplink transmission tothe infrastructure equipment in the determined resources.

Grant-free resource can be configured for multiple UEs and hencecontention may occur. Therefore in another arrangement, the uplinkresources where explicit HARQ-ACK is used are indicated by the network,i.e. RRC configured. The RRC configuration for the e-HARQ Indicatorincludes the subset of grant-free resources where explicit HARQ isenabled. Hence a UE with URLLC transmission will use these grant-freeresources in order to receive an explicit HARQ-ACK. In other words, thecommunications device is configured to receive an RRC configurationmessage from the infrastructure equipment, the RRC configuration messagecomprising an indication of a subset of the resources of the wirelessaccess interface in which a HARQ-ACK may be transmitted by theinfrastructure equipment.

In another arrangement for grant-free PUSCH transmission, the e-HARQIndicator is derived from the PUSCH transmission parameters. That iswhether the UE should monitor for an explicit HARQ-ACK depends on thecharacteristics of its PUSCH transmission. In other words, thecontroller circuitry is configured to control the transceiver circuitryto determine whether or not the communications device should monitor forthe first HARQ acknowledgement, HARQ-ACK, in a specific time slot and ina specific frequency resource of the wireless access interface dependenton a characteristic of the uplink transmission by the communicationsdevice to the infrastructure equipment in the determined resources.

In another arrangement, the said PUSCH characteristic used for e-HARQIndication in grant-free transmission is the HARQ process ID. Similar tothe arrangement above, the RRC configures which HARQ process hasexplicit HARQ-ACK. In other words, the characteristic of the uplinktransmission is an identifier of a HARQ process used by theinfrastructure equipment to transmit a HARQ-ACK to the communicationsdevice in response to the uplink transmission.

In another arrangement, the said PUSCH characteristic used for e-HARQIndication in grant-free transmission is the TBS of the PUSCH. If theTBS is smaller than a threshold, then the UE expects an explicitHARQ-ACK. This threshold can be configured by RRC or specified in thespecifications. In other words, the characteristic of the uplinktransmission is a TBS of the uplink transmission.

In another arrangement, the e-HARQ Indicator is derived based on whetherthe UE is assigned grant-free resources or not. For example, if the UEis configured with grant-free resources, the UE derives that there is animplicit e-HARQ Indicator instructing the UE to monitor an explicituplink HARQ ACK indication. This arrangement is useful for cases whereURLLC transmissions are so latency critical that there is no time toprovide an uplink grant to the UE and hence grant-free transmissions arepreferred for URLLC. In other words, the controller circuitry isconfigured to control the transceiver circuitry to determine whether ornot the communications device should monitor for the first HARQacknowledgement, HARQ-ACK, in a specific time slot and in a specificfrequency resource of the wireless access interface dependent on whetheror not the communications device determines that the communicationsdevice has been assigned grant-free resources of the wireless accessinterface by the infrastructure equipment.

It should be appreciated by those skilled in the art that other Qprotocols to HARQ may be utilised by embodiments of the presenttechnique.

Those skilled in the art would further appreciate that suchinfrastructure equipment and/or communications devices as herein definedmay be further defined in accordance with the various arrangements andembodiments discussed in the preceding paragraphs. It would be furtherappreciated by those skilled in the art that such infrastructureequipment and communications devices as herein defined and described mayform part of communications systems other than those defined by thepresent invention.

The following numbered paragraphs provide further example aspects andfeatures of the present technique:

Paragraph 1. A communications device configured to receive data from aninfrastructure equipment of a wireless communications network, thecommunications device comprising

-   -   transceiver circuitry configured to transmit signals and to        receive signals via a wireless access interface provided by the        wireless communications network, and    -   controller circuitry configured to control the transceiver        circuitry    -   to receive an explicit uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, from the        infrastructure equipment, and    -   to determine, in accordance with the received e-HARQ indicator,        whether or not the communications device should monitor for a        first HARQ acknowledgement, HARQ-ACK, in a specific time slot        and in a specific frequency resource of the wireless access        interface, the first HARQ-ACK being transmitted by the        infrastructure equipment in response to an uplink transmission        from the communications device to the infrastructure equipment.

Paragraph 2. A communications device according to Paragraph 1, whereinthe controller circuitry is configured to control the transceivercircuitry

-   -   to receive, as downlink control information, DCI, from the        infrastructure equipment, an uplink grant indicating resources        of the wireless access interface that the communications device        should use for the uplink transmission to the infrastructure        equipment,    -   wherein the uplink grant comprises the e-HARQ indicator.

Paragraph 3. A communications device according to Paragraph 1 orParagraph 2, wherein the controller circuitry is configured to controlthe transceiver circuitry

-   -   to receive, as group common DCI from the infrastructure        equipment, a Slot Format Indicator indicating a configuration of        one or more time divided slots of a wireless access interface        provided by the wireless communications network for transmitting        data to the communications device on the downlink or receiving        data from the communications device on the uplink,    -   wherein the Slot Format Indicator comprises the e-HARQ        indicator.

Paragraph 4. A communications device according to any of Paragraphs 1 to3, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to receive a radio resource control, RRC, configuration message        from the wireless communications network, the RRC configuration        message comprising the e-HARQ indicator.

Paragraph 5. A communications device according to Paragraph 4, whereinthe controller circuitry is configured to control the transceivercircuitry

-   -   to receive, from the infrastructure equipment, an SFI, the SFI        indicating a configuration of one or more time divided slots of        a wireless access interface provided by the wireless        communications network for transmitting data to the        communications device on the downlink or receiving data from the        communications device on the uplink,    -   wherein the SFI is provided by one of the RRC configuration        message, an SFI communicated in a group communications channel        and DCI, and    -   wherein the received e-HARQ indicator is dependent on at least        one parameter of the received SFI.

Paragraph 6. A communications device according to Paragraph 5, whereinthe at least one parameter of the received SFI is the configuration ofthe one or more time divided slots of the wireless access interface.

Paragraph 7. A communications device according to any of Paragraphs 4 to6, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to receive, from the infrastructure equipment, an uplink grant        indicating resources of the wireless access interface that the        communications device should use for the uplink transmission to        the infrastructure equipment,    -   wherein the received e-HARQ indicator is dependent on at least        one parameter of the received uplink grant.

Paragraph 8. A communications device according to Paragraph 7, whereinthe at least one parameter of the received uplink grant is an identifierof a HARQ process used by the infrastructure equipment to transmit aHARQ-ACK to the communications device in response to the uplinktransmission.

Paragraph 9. A communications device according to Paragraph 7 orParagraph 8, wherein the at least one parameter of the received uplinkgrant is a time delay between the transmission of the uplink grant bythe infrastructure equipment and the transmission of the uplinktransmission by the communications device.

Paragraph 10. A communications device according to any of Paragraphs 7to 9, wherein the at least one parameter of the received uplink grant isa transport block size, TBS, scheduled by the uplink grant.

Paragraph 11. A communications device according to any of Paragraphs 7to 10, wherein the at least one parameter of the received uplink grantis a granularity used by the communications device to monitor thewireless access interface for the uplink grant from the infrastructureequipment.

Paragraph 12. A communications device according to Paragraph 11, whereinthe granularity is determined in accordance with a transmission timeinterval, TTI, of the wireless communications network.

Paragraph 13. A communications device according to any of Paragraphs 1to 12, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to determine whether or not the communications device has        received a second HARQ-ACK from the infrastructure equipment in        response to the uplink transmission, and    -   to monitor for the first HARQ-ACK in the specific time slot and        in the specific frequency resource of the wireless access        interface in accordance with the received e-HARQ indicator only        if the communications device has not received the second        HARQ-ACK.

Paragraph 14. A communications device according to any of Paragraphs 1to 13, wherein the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK is predetermined and is known tothe communications device.

Paragraph 15. A communications device according to any of Paragraphs 1to 14, wherein the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK is indicated in an RRCconfiguration message received by the communications device from theinfrastructure equipment.

Paragraph 16. A communications device according to any of Paragraphs 1to 15, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to receive, from the infrastructure equipment, an uplink grant        indicating resources of the wireless access interface that the        communications device should use for the uplink transmission to        the infrastructure equipment,    -   wherein the specific time slot in which the communications        device should monitor for the first HARQ-ACK is indicated in the        uplink grant.

Paragraph 17. A communications device according to any of Paragraphs 1to 16, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to determine the specific time slot in which the communications        device should monitor for the first HARQ-ACK in accordance with        a time delay between the transmission of the uplink grant by the        infrastructure equipment and the transmission of the uplink        transmission by the communications device.

Paragraph 18. A communications device according to any of Paragraphs 1to 17, wherein the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK is one of a plurality ofconsecutive time slots forming a time window, and the communicationsdevice is configured to monitor one or more of the plurality ofconsecutive time slots of the time window for the first HARQ-ACK.

Paragraph 19. A communications device according to any of Paragraphs 1to 18, wherein the specific frequency resource in which thecommunications device should monitor for the first HARQ-ACK is indicatedin an RRC configuration message received by the communications devicefrom the infrastructure equipment.

Paragraph 20. A communications device according to Paragraph 19, whereinthe specific frequency resource in which the communications deviceshould monitor for the first HARQ-ACK contains a physical hybrid ARQindicator channel, PHICH,

-   -   wherein the PHICH comprises a single bit indicating a positive        acknowledgement or a negative acknowledgement.

Paragraph 21. A communications device according to Paragraph 19 orParagraph 20, wherein the specific frequency resource in which thecommunications device should monitor for the first HARQ-ACK contains anuplink grant indicating resources of the wireless access interface thatthe communications device should use for the uplink transmission to theinfrastructure equipment.

Paragraph 22. A communications device according to any of Paragraphs 1to 21, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to monitor for the first HARQ acknowledgement, HARQ-ACK, in a        first specific time slot and in a first specific frequency        resource of the wireless access interface, and to monitor for        the first HARQ acknowledgement, HARQ-ACK, in a second specific        time slot and in a second specific frequency resource of the        wireless access interface,    -   wherein the first specific frequency resource contains a PHICH        comprising a single bit indicating a positive acknowledgement or        a negative acknowledgement, and    -   wherein the second specific frequency contains an uplink grant        indicating resources of the wireless access interface that the        communications device should use for the uplink transmission to        the infrastructure equipment.

Paragraph 23. A communications device according to any of Paragraphs 1to 22, wherein the specific frequency resource in which thecommunications device should monitor for the first HARQ-ACK is one of aplurality of frequency resources, and the communications device isconfigured to monitor each of the plurality of frequency resources forthe first HARQ-ACK.

Paragraph 24. A communications device according to Paragraph 23, whereinif one or more of the plurality of frequency resources comprise anegative acknowledgement, the communications device is configure tore-transmit the uplink transmission to the infrastructure equipment.

Paragraph 25. A communications device according to Paragraph 23 orParagraph 24, wherein if all of the plurality of frequency resourcescomprise a positive acknowledgement, the communications device isconfigured to clear the data transmitted as the uplink transmission froma buffer of the communications device.

Paragraph 26. A communications device according to any of Paragraphs 23to 25, wherein the communications device is configured to perform a softcombining process on the plurality of frequency resources.

Paragraph 27. A communications device according to any of Paragraphs 1to 26, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to determine that the communications device has been assigned        grant-free resources of the wireless access interface by the        infrastructure equipment,    -   to determine, without reception of an uplink grant from the        infrastructure equipment, resources of the grant-free resources        of the wireless access interface that the communications device        should use for the uplink transmission to the infrastructure        equipment, and    -   to transmit the uplink transmission to the infrastructure        equipment in the determined resources.

Paragraph 28. A communications device according to Paragraph 27, whereinthe communications device is configured to receive an RRC configurationmessage from the infrastructure equipment, the RRC configuration messagecomprising an indication of a subset of the resources of the wirelessaccess interface in which the first HARQ-ACK may be transmitted by theinfrastructure equipment.

Paragraph 29. A communications device according to Paragraph 27 orParagraph 28, wherein the controller circuitry is configured to controlthe transceiver circuitry

-   -   to determine whether or not the communications device should        monitor for the first HARQ acknowledgement, HARQ-ACK, in a        specific time slot and in a specific frequency resource of the        wireless access interface dependent on a characteristic of the        uplink transmission by the communications device to the        infrastructure equipment in the determined resources.

Paragraph 30. A communications device according to Paragraph 29, whereinthe characteristic of the uplink transmission is an identifier of a HARQprocess used by the infrastructure equipment to transmit a HARQ-ACK tothe communications device in response to the uplink transmission.

Paragraph 31. A communications device according to Paragraph 29 orParagraph 30, wherein the characteristic of the uplink transmission is aTBS of the uplink transmission.

Paragraph 32. A communications device according to any of Paragraphs 27to 31, wherein the controller circuitry is configured to control thetransceiver circuitry

-   -   to determine whether or not the communications device should        monitor for the first HARQ acknowledgement, HARQ-ACK, in a        specific time slot and in a specific frequency resource of the        wireless access interface dependent on whether or not the        communications device determines that the communications device        has been assigned grant-free resources of the wireless access        interface by the infrastructure equipment.

Paragraph 33. A method of operating a communications device configuredto receive data from an infrastructure equipment of a wirelesscommunications network, the method comprising

-   -   receiving an explicit uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, from the        infrastructure equipment, and    -   determining, in accordance with the received e-HARQ indicator,        whether or not the communications device should monitor for a        first HARQ acknowledgement, HARQ-ACK, in a specific time slot        and in a specific frequency resource of a wireless access        interface provided by the wireless communications network, the        first HARQ-ACK being transmitted by the infrastructure equipment        in response to an uplink transmission from the communications        device to the infrastructure equipment.

Paragraph 34. Circuitry for a communications device configured toreceive data from an infrastructure equipment of a wirelesscommunications network, the communications device comprising

-   -   transceiver circuitry configured to transmit signals and to        receive signals via a wireless access interface provided by the        wireless communications network, and    -   controller circuitry configured to control the transceiver        circuitry    -   to receive explicit an uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, from the        infrastructure equipment, and    -   to determine, in accordance with the received e-HARQ indicator,        whether or not the communications device should monitor for a        first HARQ acknowledgement, HARQ-ACK, in a specific time slot        and in a specific frequency resource of the wireless access        interface, the first HARQ-ACK being transmitted by the        infrastructure equipment in response to an uplink transmission        from the communications device to the infrastructure equipment.

Paragraph 35. An infrastructure equipment forming part of a wirelesscommunications network, the infrastructure equipment comprising

-   -   transceiver circuitry configured to transmit signals and to        receive signals via a wireless access interface provided by the        wireless communications network, and    -   controller circuitry configured to control the transceiver        circuitry    -   to transmit an explicit uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, to a communications        device,    -   wherein the e-HARQ indicator indicates to the communications        device whether or not the communications device should monitor        for a first HARQ acknowledgement, HARQ-ACK, in a specific time        slot and in a specific frequency resource of the wireless access        interface, the first HARQ-ACK being transmitted by the        infrastructure equipment in response to an uplink transmission        from the communications device to the infrastructure equipment.

Paragraph 36. A method of operating an infrastructure equipment formingpart of a wireless communications network, the method comprising

-   -   transmitting an explicit uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, to a communications        device,    -   wherein the e-HARQ indicator indicates to the communications        device whether or not the communications device should monitor        for a first HARQ acknowledgement, HARQ-ACK, in a specific time        slot and in a specific frequency resource of a wireless access        interface provided by the wireless communications network, the        first HARQ-ACK being transmitted by the infrastructure equipment        in response to an uplink transmission from the communications        device to the infrastructure equipment.

Paragraph 37. Circuitry for an infrastructure equipment forming part ofa wireless communications network, the infrastructure equipmentcomprising

-   -   transceiver circuitry configured to transmit signals and to        receive signals via a wireless access interface provided by the        wireless communications network, and    -   controller circuitry configured to control the transceiver        circuitry    -   to transmit an explicit uplink hybrid automatic repeat request        acknowledgement indicator, e-HARQ indicator, to a communications        device,

wherein the e-HARQ indicator indicates to the communications devicewhether or not the communications device should monitor for a first HARQacknowledgement, HARQ-ACK, in a specific time slot and in a specificfrequency resource of the wireless access interface, the first HARQ-ACKbeing transmitted by the infrastructure equipment in response to anuplink transmission from the communications device to the infrastructureequipment.

In so far as embodiments of the disclosure have been described as beingimplemented, at least in part, by software-controlled data processingapparatus, it will be appreciated that a non-transitory machine-readablemedium carrying such software, such as an optical disk, a magnetic disk,semiconductor memory or the like, is also considered to represent anembodiment of the present disclosure.

It will be appreciated that the above description for clarity hasdescribed embodiments with reference to different functional units,circuitry and/or processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits, circuitry and/or processors may be used without detracting fromthe embodiments.

Described embodiments may be implemented in any suitable form includinghardware, software, firmware or any combination of these. Describedembodiments may optionally be implemented at least partly as computersoftware running on one or more data processors and/or digital signalprocessors. The elements and components of any embodiment may bephysically, functionally and logically implemented in any suitable way.Indeed the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units. As such, thedisclosed embodiments may be implemented in a single unit or may bephysically and functionally distributed between different units,circuitry and/or processors.

Although the present disclosure has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Additionally, although a feature may appear to bedescribed in connection with particular embodiments, one skilled in theart would recognise that various features of the described embodimentsmay be combined in any manner suitable to implement the technique.

REFERENCES

[1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radioaccess”, John Wiley and Sons, 2009.

[2] RP-172834, “Revised WID on New Radio Access Technology,” NTT DOCOMO,#78.

[3] TR 38.913, “Study on Scenarios and Requirements for Next GenerationAccess Technologies (Release 14)”.

1. A communications device configured to receive data from aninfrastructure equipment of a wireless communications network, thecommunications device comprising transceiver circuitry configured totransmit signals and to receive signals via a wireless access interfaceprovided by the wireless communications network, and controllercircuitry configured to control the transceiver circuitry to receive anexplicit uplink hybrid automatic repeat request acknowledgementindicator, e-HARQ indicator, from the infrastructure equipment, and todetermine, in accordance with the received e-HARQ indicator, whether ornot the communications device should monitor for a first HARQacknowledgement, HARQ-ACK, in a specific time slot and in a specificfrequency resource of the wireless access interface, the first HARQ-ACKbeing transmitted by the infrastructure equipment in response to anuplink transmission from the communications device to the infrastructureequipment.
 2. A communications device according to claim 1, wherein thecontroller circuitry is configured to control the transceiver circuitryto receive, as downlink control information, DCI, from theinfrastructure equipment, an uplink grant indicating resources of thewireless access interface that the communications device should use forthe uplink transmission to the infrastructure equipment, wherein theuplink grant comprises the e-HARQ indicator.
 3. A communications deviceaccording to claim 1, wherein the controller circuitry is configured tocontrol the transceiver circuitry to receive, as group common DCI fromthe infrastructure equipment, a Slot Format Indicator indicating aconfiguration of one or more time divided slots of a wireless accessinterface provided by the wireless communications network fortransmitting data to the communications device on the downlink orreceiving data from the communications device on the uplink, wherein theSlot Format Indicator comprises the e-HARQ indicator.
 4. Acommunications device according to claim 1, wherein the controllercircuitry is configured to control the transceiver circuitry to receivea radio resource control, RRC, configuration message from the wirelesscommunications network, the RRC configuration message comprising thee-HARQ indicator.
 5. A communications device according to claim 4,wherein the controller circuitry is configured to control thetransceiver circuitry to receive, from the infrastructure equipment, anSFI, the SFI indicating a configuration of one or more time dividedslots of a wireless access interface provided by the wirelesscommunications network for transmitting data to the communicationsdevice on the downlink or receiving data from the communications deviceon the uplink, wherein the SFI is provided by one of the RRCconfiguration message, an SFI communicated in a group communicationschannel and DCI, and wherein the received e-HARQ indicator is dependenton at least one parameter of the received SFI.
 6. A communicationsdevice according to claim 5, wherein the at least one parameter of thereceived SFI is the configuration of the one or more time divided slotsof the wireless access interface.
 7. A communications device accordingto claim 4, wherein the controller circuitry is configured to controlthe transceiver circuitry to receive, from the infrastructure equipment,an uplink grant indicating resources of the wireless access interfacethat the communications device should use for the uplink transmission tothe infrastructure equipment, wherein the received e-HARQ indicator isdependent on at least one parameter of the received uplink grant.
 8. Acommunications device according to claim 7, wherein the at least oneparameter of the received uplink grant is an identifier of a HARQprocess used by the infrastructure equipment to transmit a HARQ-ACK tothe communications device in response to the uplink transmission.
 9. Acommunications device according to claim 7, wherein the at least oneparameter of the received uplink grant is a time delay between thetransmission of the uplink grant by the infrastructure equipment and thetransmission of the uplink transmission by the communications device.10. A communications device according to claim 7, wherein the at leastone parameter of the received uplink grant is a transport block size,TBS, scheduled by the uplink grant.
 11. A communications deviceaccording to claim 7, wherein the at least one parameter of the receiveduplink grant is a granularity used by the communications device tomonitor the wireless access interface for the uplink grant from theinfrastructure equipment.
 12. (canceled)
 13. A communications deviceaccording to claim 1, wherein the controller circuitry is configured tocontrol the transceiver circuitry to determine whether or not thecommunications device has received a second HARQ-ACK from theinfrastructure equipment in response to the uplink transmission, and tomonitor for the first HARQ-ACK in the specific time slot and in thespecific frequency resource of the wireless access interface inaccordance with the received e-HARQ indicator only if the communicationsdevice has not received the second HARQ-ACK.
 14. A communications deviceaccording to claim 1, wherein the specific time slot in which thecommunications device should monitor for the first HARQ-ACK ispredetermined and is known to the communications device.
 15. Acommunications device according to claim 1, wherein the specific timeslot in which the communications device should monitor for the firstHARQ-ACK is indicated in an RRC configuration message received by thecommunications device from the infrastructure equipment.
 16. Acommunications device according to claim 1, wherein the controllercircuitry is configured to control the transceiver circuitry to receive,from the infrastructure equipment, an uplink grant indicating resourcesof the wireless access interface that the communications device shoulduse for the uplink transmission to the infrastructure equipment, whereinthe specific time slot in which the communications device should monitorfor the first HARQ-ACK is indicated in the uplink grant.
 17. Acommunications device according to claim 1, wherein the controllercircuitry is configured to control the transceiver circuitry todetermine the specific time slot in which the communications deviceshould monitor for the first HARQ-ACK in accordance with a time delaybetween the transmission of the uplink grant by the infrastructureequipment and the transmission of the uplink transmission by thecommunications device.
 18. A communications device according to claim 1,wherein the specific time slot in which the communications device shouldmonitor for the first HARQ-ACK is one of a plurality of consecutive timeslots forming a time window, and the communications device is configuredto monitor one or more of the plurality of consecutive time slots of thetime window for the first HARQ-ACK.
 19. A communications deviceaccording to claim 1, wherein the specific frequency resource in whichthe communications device should monitor for the first HARQ-ACK isindicated in an RRC configuration message received by the communicationsdevice from the infrastructure equipment. 20.-32. (canceled)
 33. Amethod of operating a communications device configured to receive datafrom an infrastructure equipment of a wireless communications network,the method comprising receiving an explicit uplink hybrid automaticrepeat request acknowledgement indicator, e-HARQ indicator, from theinfrastructure equipment, and determining, in accordance with thereceived e-HARQ indicator, whether or not the communications deviceshould monitor for a first HARQ acknowledgement, HARQ-ACK, in a specifictime slot and in a specific frequency resource of a wireless accessinterface provided by the wireless communications network, the firstHARQ-ACK being transmitted by the infrastructure equipment in responseto an uplink transmission from the communications device to theinfrastructure equipment.
 34. Circuitry for a communications deviceconfigured to receive data from an infrastructure equipment of awireless communications network, the communications device comprisingtransceiver circuitry configured to transmit signals and to receivesignals via a wireless access interface provided by the wirelesscommunications network, and controller circuitry configured to controlthe transceiver circuitry to receive explicit an uplink hybrid automaticrepeat request acknowledgement indicator, e-HARQ indicator, from theinfrastructure equipment, and to determine, in accordance with thereceived e-HARQ indicator, whether or not the communications deviceshould monitor for a first HARQ acknowledgement, HARQ-ACK, in a specifictime slot and in a specific frequency resource of the wireless accessinterface, the first HARQ-ACK being transmitted by the infrastructureequipment in response to an uplink transmission from the communicationsdevice to the infrastructure equipment. 35.-37. (canceled)